1. Field of the Invention
This invention relates to a controller of an elevator of an energy saving type to which a secondary battery is applied.
2. Description of the Related Art
FIG. 10 is a view showing the basic construction of a controller for controlling the operation of an elevator by applying a conventional secondary battery thereto.
In FIG. 10, reference numerals 1 and 2 respectively designate a three-phase AC power source and a converter constructed by a diode, etc. and converting AC power outputted from the three-phase AC power source 1 to DC power. The DC power converted by the converter 2 is supplied to a DC bus 3. The operation of an inverter 4 is controlled by a speed controller for controlling a speed position of the elevator and described later. A direct current supplied through the DC bus 3 is converted to an alternating current of predetermined desirable variable voltage and variable frequency and an AC motor 5 is driven so that a hoisting machine 6 of the elevator directly connected to the AC motor 5 is rotated. Thus, a rope 7 wound around the hoisting machine 6 controls elevating and lowering operations of a car 8 and a counterweight 9 connected to both ends of this rope 7 and passengers within the car 8 are moved to a predetermined stage floor.
Here, weights of the car 8 and the counterweight 9 are designed such that these weights are approximately equal to each other when passengers half a number limit ride in the car 8. Namely, when the car 8 is elevated and lowered with no load, a power running operation is performed at a lowering time of the car 8 and a regenerative operation is performed at a elevating time of the car 8. Conversely, when the car 8 is lowered in the number limit riding, the regenerative operation is performed at the lowering time of the car 8 and the power running operation is performed at the elevating time of the car 8.
An elevator control circuit 10 is constructed by a microcomputer, etc., and manages and controls an entire operation of the elevator. A power accumulating device 11 is arranged between DC buses 3 and accumulates power at the regenerative operation time of the elevator, and supplies the accumulated power to the inverter 4 together with the converter 2 at the power running operation time. The power accumulating device 11 is constructed by a secondary battery 12 and a DC-DC converter 13 for controlling charging and discharging operations of this secondary battery 12.
Here, the DC-DC converter 13 has a voltage lowering type chopper circuit and a voltage raising type chopper circuit. The voltage lowering type chopper circuit is constructed by a reactor 13a, a gate 13b for charging current control connected in series to this reactor 13a, and a diode 13c connected in reverse parallel to a gate 13d for discharging current control described later. The voltage raising type chopper circuit is constructed by the reactor 13a, the gate 13d for discharging current control connected in series to this reactor 13a, and a diode 13e connected in reverse parallel to the above gate 13b for charging current control. Operations of the gate 13b for charging current control and the gate 13d for discharging current control are controlled by a charging-discharging control circuit 15 on the basis of a measuring value from a charging-discharging state measuring device 14 for measuring charging and discharging states of the power accumulating device 11 and a measuring value from a voltage measuring instrument 18. A current measuring instrument arranged between the secondary battery 12 and the DC-DC converter 13 is used as the charging-discharging state measuring device 14 in this conventional example.
A gate 16 for regenerative current control and a regenerative resistor 17 are arranged between DC buses 3. The voltage measuring instrument 18 measures the voltage of a DC bus 3. A regenerative control circuit 19 is operated on the basis of regenerative control commands from a speed control circuit described later. The gate 16 for regenerative current control is constructed such that an ON pulse width is controlled on the basis of control of the regenerative control circuit 19 when a measuring voltage provided by the voltage measuring instrument 17 is equal to or greater than a predetermined value at the regenerative operation time. Regenerated power is discharged in the regenerative resistor 17 and is converted to thermal energy and is consumed.
An encoder 20 is directly connected to the hoisting machine 6. The speed control circuit 21 controls a position and a speed of the elevator by controlling an output voltage and an output frequency of the inverter 4 on the basis of speed commands and a speed feedback output from the encoder 22 based on commands from the elevator control circuit 10.
An operation of the controller having the above construction will next be explained.
At a power running operation time of the elevator, power is supplied to the inverter 4 from both the three-phase AC power source 1 and the power accumulating device 11. The power accumulating device 11 is constructed by the secondary battery 12 and the DC-DC converter 13, and an operation of this power accumulating device 11 is controlled by the charging-discharging control circuit 15. In general, the number of secondary batteries 12 is reduced as much as possible and an output voltage of each secondary battery 12 is lower than the voltage of the DC bus 3 so as to make the controller compact and cheaply construct the controller. The voltage of the DC bus 3 is basically controlled near a voltage provided by rectifying a three-phase AC of the three-phase AC power source 1. Accordingly, it is necessary to lower the bus voltage of the DC bus 3 at a charging time of the secondary battery 12 and raise the bus voltage of the DC bus 3 at a discharging time of the secondary battery 12. Therefore, the DC-DC converter 13 is adopted. Operations of the gate 13b for charging current control and the gate 13d for discharging current control in this DC-DC converter 13 are controlled by the charging-discharging control circuit 15.
FIGS. 11 and 12 are flow charts showing controls of the charging-discharging control circuit 15 at its discharging and charging times.
The control of the charging-discharging control circuit 15 at the discharging time shown in FIG. 11 will first be explained.
A current control minor loop, etc. are constructed in voltage control of a control system and the control operation may be more stably performed. However, for simplicity, the control of the charging-discharging control circuit 15 is here explained by a control system using the bus voltage.
First, the bus voltage of the DC bus 3 is measured by the voltage measuring instrument 17 (step S11). The charging-discharging control circuit 15 compares this measuring voltage with a predetermined desirable voltage set value and judges whether the measuring voltage exceeds the voltage set value or not (step S12). If no measuring voltage exceeds the set value, the charging-discharging control circuit 15 next judges whether the measuring value of a discharging current of the secondary battery 12 provided by the charging-discharging state measuring device 14 exceeds a predetermined value or not (step S13).
When the measuring voltage exceeds the set value by these judgments, or when the measuring value of the discharging current of the secondary battery 12 exceeds the predetermined value even if no measuring voltage exceeds the set value, an adjusting time DT is subtracted from the present ON time to shorten an ON pulse width of the gate 13d for discharging current control and a new gate ON time is calculated (step S14).
In contrast to this, when it is judged in the above step S13 that no measuring value of the discharging current of the secondary battery 12 provided by the measuring device 14 exceeds the predetermined value, a new gate ON time is calculated by adding the adjusting time DT to the present ON time so as to lengthen the ON pulse width of the gate 13d for discharging current control (step S15). Thus, ON control of the gate 13d for discharging current control is performed on the basis of the calculated gate ON time, and the calculated gate ON time is stored to a built-in memory as the present ON time (step S16).
Thus, more electric current flows from the secondary battery 12 by lengthening the ON pulse width of the gate 13d for discharging current control. As a result, supply power is increased and the bus voltage of the DC bus 3 is increased by power. When the power running operation is considered, the elevator requires the power supply and this power is supplied by discharging the secondary battery 12 and by the three-phase AC power source 1. When the bus voltage is controlled such that this bus voltage is higher than an output voltage of the converter 2 supplied from the three-phase AC power source 1, all power is supplied from the secondary battery 12. However, the controller is designed such that all power is not supplied from the secondary battery 12, but is supplied from the secondary battery 12 and the three-phase AC power source 1 in a suitable ratio so as to cheaply construct the power accumulating device 11.
Namely, in FIG. 11, the measuring value of the discharging current is compared with a supply allotment corresponding current (predetermined value). If this measuring value exceeds the predetermined value, the ON pulse width of the gate 13d for discharging current control is lengthened and a supply amount is further increased. In contrast to this, when no measuring value of the discharging current exceeds the predetermined value, the ON pulse width of the gate 13d for discharging current control is shortened and the power supply is clipped. Thus, since power supplied from the secondary battery 12 is clipped among power required in the inverter 4, the bus voltage of the DC bus 3 is reduced so that the power supply from the converter 2 is started. These operations are performed for a very short time so that a suitable bus voltage is actually obtained to supply required power of the elevator. Thus, power can be supplied from the secondary battery 12 and the three-phase AC power source 1 in a predetermined desirable ratio.
The control of the charging-discharging control circuit 15 at the charging time shown in FIG. 12 will next be explained.
When there is power regeneration from the AC motor 5, the bus voltage of the DC bus 3 is increased by this regenerated power. When this voltage is higher than an output voltage of the converter 2, the power supply from the three-phase AC power source 1 is stopped. When there is no power accumulating device 11 and this stopping state is continued, the voltage of the DC bus 3 is increased. Therefore, when a measuring voltage value of the voltage measuring instrument 17 for detecting the bus voltage of the DC bus 3 reaches a certain predetermined voltage, the regenerative control circuit 19 is operated and closes the gate 16 for regenerative current control. Thus, power flows through the regenerative resistor 17 and the regenerated power is consumed and the elevator is decelerated by electromagnetic braking effects. However, when there is the power accumulating device 11, this power is charged to the power accumulating device 11 by the control of the charging-discharging control circuit 15 with a voltage equal to or smaller than a predetermined voltage.
Namely, as shown in FIG. 12, if the measuring value of the bus voltage of the DC bus 3 provided by the voltage measuring instrument 17 exceeds the predetermined voltage, the charging-discharging control circuit 15 detects that it is a regenerative state, and increases a charging current to the secondary battery 12 by lengthening the ON pulse width of the gate 13b for charging current control (step S21xe2x86x92S22xe2x86x92S23). When the regenerated power from the elevator is reduced in a short time, the voltage of the DC bus 3 is also correspondingly reduced and no measuring value of the voltage measuring instrument 17 exceeds the predetermined voltage. Accordingly, the ON pulse width of the gate 13b for charging current control is shortly controlled and charging power is also reduced and controlled (step S21xe2x86x92S22xe2x86x92S24).
Thus, the bus voltage is controlled in a suitable range and a charging operation is performed by monitoring the bus voltage of the DC bus 3 and controlling the charging power. Further, energy is saved by accumulating and re-utilizing power conventionally consumed in the regenerated power. When no power of a charger is consumed for certain reasons such as a breakdown, etc., the above regenerative control circuit 19 is operated as a backup and the regenerated power is consumed by a resistor so that the elevator is suitably decelerated. In a general elevator for housing, the regenerated power is about 2 KVA and is about 4 KVA at its maximum decelerating value although this regenerated power is different in accordance with a capacity of the elevator, etc.
The regenerative control circuit 19 monitors the voltage of the DC bus 3. If this voltage is equal to or greater than a predetermined value, the ON pulse width of the gate 16 for regenerative current control is controlled by the regenerative control circuit 19 so as to discharge the above power in the regenerative resistor 17 so that the regenerated power flows through the regenerative resistor 17. There are various kinds of systems for controlling this pulse width, but the pulse width is simply controlled in accordance with the following formula. Namely, when the voltage of the DC bus 3 for starting turning-on of the gate 16 for regenerative current control is set to VR, a flowing current IR can be simply calculated by turning-on (closing) a circuit since a resistance value of the regenerative resistor 17 is already known. Further, maximum power to be flowed is already known. Therefore, if this maximum power (VA) is set to WR, it is sufficient to generate an ON pulse of duty of WR/(VRxc3x97IR) while the DC bus voltage is monitored. However, an object of this construction is to consume all regenerated power in the regenerative resistor 17.
However, the power accumulating device 11 is cheaply constructed in the above conventional controller of the elevator. Therefore, when the power accumulating device 11 is capable of supplying power sufficient to operate the elevator in any load condition upon failure of commercial power, this power accumulating device becomes expensive. Accordingly, when there is no supply of the commercial power upon a power failure, it is impossible to sufficiently supply operating power for the elevator requiring maximum running power for up-driving with a full load. Therefore, the elevator must be operated at a low speed at which the elevator can run in all operating modes.
To solve the above problems, an object of this invention is to provide a controller of an elevator capable of performing smooth speed control even during a power failure, using a cheap power accumulating device having a low capacity.
To achieve this object, a controller of an elevator in this invention comprises a converter for rectifying AC power from an AC power source and converting the AC power to DC power; an inverter for converting the DC power from the converter to AC power of a variable voltage and a variable frequency and driving an electric motor and operating the elevator; a power accumulating device arranged between DC buses between the converter and the inverter, and accumulating DC power from the DC buses at a regenerative operation time of the elevator, and supplying the accumulated DC power at a power running operation time to the DC buses; a charging-discharging control device for controlling charging and discharging operations of the power accumulating device with respect to the DC buses; power failure detecting means for detecting a power failure; current detecting means for detecting an output current of the inverter; voltage detecting means for detecting an output voltage of the inverter; car load measuring means arranged in a car of the elevator and measuring a car load; speed detecting means for detecting an operating speed of the elevator; and speed control means for controlling an operation of the inverter to perform speed control based on speed commands and a detecting value provided by the speed detecting means of the elevator; the controller being characterized in that the speed control means has a table set with required power in accordance with the speed and the car load; and output power of the inverter is calculated on the basis of a detected current value of the current detecting means and a detected voltage value of the voltage detecting means at a time of power failure detection using the power failure detecting means; and the required power is calculated from the table on the basis of a car load measuring value measured by the car load measuring means and a detecting speed detected by the speed detecting means; and the speed commands for performing the speed control are calculated within a range of discharging ability power on the basis of comparison of the calculated output power of the inverter, the calculated required power and the discharging ability power of the power accumulating device.
Further, a fixed value is set as the discharging ability power of the power accumulating device in the speed control means.
Further, the controller further comprises charging-discharging state measuring means for measuring at least one of a temperature, charging and discharging currents and charging and discharging voltages of the power accumulating device, and the speed control means has a table set with a limited discharging current with respect to the discharging current and the discharging voltage, and the limited discharging current is calculated from the table on the basis of measuring values of the discharging current and the discharging voltage from the charging-discharging state measuring means, and the discharging ability power of the power accumulating device is calculated from the calculated limited discharging current and the measuring value of the discharging voltage.
Further, the speed control means has a table set with the limited discharging current with respect to the temperature, and the limited discharging current is calculated from the table on the basis of a measuring value of the temperature from the charging-discharging state measuring means, and the discharging ability power of the power accumulating device is calculated from the calculated limited discharging current and the measuring value of the discharging voltage.
Further, the speed control means has a table set with the limited discharging current with respect to a charging degree as a value obtained by normalizing and accumulating a product of a charging-discharging current and a charging-discharging voltage by a capacity with a full charging state of the power accumulating device as a reference, and the limited discharging current is calculated from the table on the basis of the charging degree obtained on the basis of the measuring values of the discharging current and the discharging voltage from the charging-discharging state measuring means, and the discharging ability power of the power accumulating device is calculated from the calculated limited discharging current and the measuring value of the discharging voltage.
Further, the speed control means has a table set with a speed pattern in accordance with a load state, and the speed pattern is calculated from the table on the basis of a car load measuring value measured by the car load measuring means, and the speed commands according to the calculated speed pattern are generated.
Further, the power failure detecting means detects the power failure of the AC power source.
Further, the power failure detecting means detects the power failure on the basis of a detecting voltage of the DC buses.
Further, the speed control means continues acceleration if the elevator is accelerated when the discharging ability power is larger than the output power of the inverter.